<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link id="lk" rel="stylesheet" href="css/1.css">
</head>
<body>
    <div class="box">
        <button>皮肤1</button>
        <button>皮肤2</button>
    </div>
    <script>
        oBtns=document.querySelectorAll("button");
        oBox=document.querySelector("box");
        oLk=document.querySelector("#lk");

        oBtns[0].onclick=function(){
            oLk.href="css/1.css";
        }
        oBtns[1].onclick=function(){
            oLk.href="css/2.css";
        }
    </script>
</body>
</html>